Apparatuses of the species are known in particular from the field of microscopy, where such apparatuses are used as objective turrets or as filter magazines. In the one case the receiving device is a turret, mounted rotatably about an axis, in which various microscope objectives are inserted. In the other case, especially in fluorescence microscopy, the receiving device is embodied as a positionable filter magazine that is likewise rotatable about an axis or movable in a linear direction, optionally in motorized fashion. If the turret is driven in motorized fashion, but also in the case of manual rotation of the turret, it is necessary, for example in order to adjust illumination aperture diaphragms or filters in the optical beam path of the microscope for microscope control purposes, to be able to determine the position in which the turret is currently located, and thus to know which objective is positioned in the beam path of the microscope.
A number of coding and detection means are known from the existing art for this purpose. Reference will be made merely by way of example to DE 37 11 843 A1, from which a turret rotation device for optical components is known. For detection of the current position of the turret rotation device, a total of five sensors or detectors are provided there, detecting different coding means of the coding device provided there. The detectors are arranged in such a way that they each detect the coding device at radially and/or circumferentially different points. The detectors and coding means encompass on the one hand a light barrier that detects a slit, and on the other hand four light barriers that detect light which is reflected from highly reflective strip-shaped coatings that are arranged on the turret rotation device. The coding means or coding device is associated with the receiving device, and the detectors are mounted in stationary fashion on the microscope stand. Detection in this context also encompasses sensing of the instantaneous rotation direction. These coding and detection means entail a high level of component complexity, along with time-consuming manufacturing and functional testing. These coding and detection means are therefore expensive, especially since many components that must be installed and aligned are required.